1. Field of the Invention
An aspect of the present invention relates to an image forming apparatus and a signal synchronizing method thereof, and more particularly, to an image forming apparatus having a plurality of optical scanning parts for scanning a photoconductor with light, and a signal synchronizing method thereof.
2. Description of the Related Art
An image forming apparatus forms a print image through various systems such as an inkjet system, an electrophotographic system or other systems known in the art. Of these systems, an image forming apparatus that employs the electrophotographic system forms an image on a recording medium through a paper feeder, an image forming part, a fixer, a paper discharger and so on.
Conventional image forming apparatuses form an electrostatic latent image on a photoconductor when an optical scanning part scans the photoconductor with light. Of the conventional image forming apparatuses, an image forming apparatus that is capable of forming an image with plural colors includes a plurality of optical scanning parts corresponding to the plural colors, each of which scans a photoconductor with light based on horizontal synchronization signals and video clock signals according to print data.
Such an image forming apparatus that is capable of forming the image with the plural colors corrects optical scanning points of different optical scanning parts based on a particular optical scanning part among the plurality of optical scanning parts. This is done in order to alleviate deviations in assembly process of the respective optical scanning parts. Thus, the plurality of optical scanning parts share one polygon mirror and scan the photoconductor with light according to the corrected optical scanning points based on horizontal synchronization signals applied to the corresponding optical scanning parts.
When the conventional image forming apparatus synchronizes video clocks and scans the photoconductors with light, if at a point of time when a horizontal synchronization signal is applied to one optical scanning part falls within non-image intervals, that is, not effective image intervals, of different optical scanning parts, it is possible to scan the photoconductor with light according to the corrected optical scanning points of time.
However, as shown in FIG. 1, if a first horizontal synchronization signal is applied in an effective image interval according to a second video clock, that is, if a horizontal synchronization signal is applied to an optical scanning part in an effective image interval in which another optical scanning part scans a photoconductor with light corresponding to an effective image, the effective image may not be correctly formed since a frequency is varied in order to re-align a direction in which the effective image is formed, as indicated by A in FIG. 1.